Coordinate global modal priority and focus

[cauyxy]

Summary

• add an app-wide modal coordinator with critical, confirmation, system, and informational priorities plus FIFO ordering
• route destructive confirmations, updater, and support payment through one active-dialog surface with explicit dismissal policies
• restore focus after dismissal and make shell disclosures controlled and keyboard-operable
• update current truth documentation and verification coverage

Testing

• npm run check
• npx vitest run src/features/shared/modalCoordinator.test.ts src/features/shared/modalCoordinator.integration.test.ts src/layouts/ShellHeader.test.tsx src/components/ui/ConfirmDialog.test.tsx
• npm run test:unit
• npm run verify -- --source-only
• macOS Tauri smoke: startup detection completed; frontend, overlay, and settings returned HTTP 200
• browser Preview: modal count/queue surfaces, Support payment focus restoration, Bilibili Escape focus restoration, route navigation, and overflow/console checks

Closes #28

Release Notes:

• 全局弹窗现在按确定优先级依次显示，并在关闭后恢复到合适的操作焦点。

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Honor FIFO when active priority is demoted

When a higher-priority modal preempts an older source and then updates down into that older source's priority, this strict > check keeps the newer modal active even though sortedEntries() would put the older queued modal first. For example, an older confirmation queued behind a critical modal remains hidden after the critical modal downgrades to confirmation, violating the documented FIFO ordering within equal priorities until the newer modal closes.

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